code: def _alpha_span_to_special_tag(span):
      r"""
      将span替换成特殊的字符
  
      :param str span:
      :return:
      """
      if "oo" == span.lower():  # speical case when represent 2OO8
          return span
      if len(span) == 1:
          return span
      else:
          return "<ENG>"
  
file_path: fastNLP/fastNLP/io/pipe/cws.py
imports: import re
  from itertools import chain
  from .pipe import Pipe
  from .utils import _indexize
  from fastNLP.io.data_bundle import DataBundle
  from fastNLP.io.loader import CWSLoader
label_desc: Use image node_id 3 for calling a global function with example usage: _alpha_span_to_special_tag(span) and returns: span, span, str